Sealing of cable trays on floors of residential buildings

Cable trays penetrating floors in residential buildings must be sealed with fire-resistant materials to restore the floor's fire integrity and prevent smoke or water ingress.

Regulatory and Safety Requirements

When cable trays pass through floors, the openings must be minimized and sealed to maintain the original fire resistance of the floor. Regulations such as Group 527. 2 require both external and internal sealing around wiring and cable containment systems, ensuring that the sealing resists fire, smoke, and water penetration to the same degree as the floor itself.

Non-flame propagating cables with small cross-sectional areas may have reduced internal sealing requirements, but external sealing is still necessary.

Materials for Sealing

Common firestopping materials for floor penetrations include: Fire-rated boards and firestop packsFirestop mastic or intumescent sealantsFire-resistant mineral woolModular systems like FIRSTO, which allow easy installation and later cable modifications For large openings, a fire-resistant backing plate or support plate should be installed before sealing to ensure stability and maintain fire resistance. Gaps around cables should be minimal, typically not exceeding 1 cm², and packing thickness should meet manufacturer specifications, often around 24 mm.

Installation Guidelines

Ensure floor finishes and electrical shafts are completed before sealing. Seal all gaps internally and externally around metal trunking or cable trays. Use cover plates of consistent dimensions to close openings neatly and maintain fire integrity.

For linear or service penetration seals, expanding intumescent materials are effective for accommodating limited movement while maintaining fire resistance. Modular systems like FIRSTO allow for easy addition or removal of cables without compromising the firestop.

Standards and Testing

Cable penetration seals should comply with European Standard EN 1366-3 and be classified according to EN 13501-2. The fire resistance of the seal depends on the cable type, configuration, and the tested cross-section. Only tested systems should be used to ensure compliance and safety.

Practical Considerations

Keep openings as small as practicable to reduce fire risk. Ensure the sealing material is resistant to combustion products and water penetration. Plan the layout to facilitate installation and future maintenance.

Consider mechanical loads and accessibility when selecting sealing systems, especially in residential buildings with multiple cable trays. By following these guidelines, cable tray penetrations through floors can maintain the fire safety, structural integrity, and regulatory compliance required in residential buildings.